Variation in female mating performance can affect the direction and rate of evolution through sexual selection. The social environment determines the availability of mates and the competitive situation, and hence can influence mating strategies. However, these effects have to be considered within time constraints. Here we show that female sand gobies exposed to same-sex competitors (female-biased adult sex ratio, ASR) for a week before having physical access to males (i.e., a delayed male access; referred as prior exposure treatment) were more actively associated with the preferred male and took faster spawning decisions. However, these females mated more frequently with males with traits that did not ensure high egg survival. On the other extreme, females exposed to low same sex competition (male-biased ASR) simultaneously to the mate choice (i.e., an immediate access to males; referred as simultaneous exposure treatment) took more time to make their spawning decision. They also associated and spawned more often with males with good parental skills (i.e., males exhibiting more egg fanning behaviour). These male traits are associated with higher survival and better development of eggs. Our results provide experimental support for a trade-off between mate choice accuracy and speed, which depended on mating competition.